UI Should show blacklisted executors & nodes

Details

Description

SPARK-8425 will add the ability to blacklist entire executors and nodes to deal w/ faulty hardware. However, without displaying it on the UI, it can be hard to realize which executor is bad, and why tasks aren't getting scheduled on certain executors.

As a first step, we should just show nodes and executors that are blacklisted for the entire application (no need to show blacklisting for tasks & stages).

This should also ensure that blacklisting events get into the event logs for the history server.